The construction of a sloped roof commonly involves the placement of a plywood sub-roof structure on roof trusses and then covering the plywood with a water resistant sheet of tar impregnated paper, generally referred to as "roofing felt" and sometimes known as "tar paper". This material is secured to the sub-roof plywood with nails. This assembly is typically covered with shingles or other conventional roofing materials to complete the roof.
Nailing the roofing felt securely to a substrate such as a wood sub-roof can be difficult. Because of the necessity to make a structure waterproof as soon as possible, the sub-roof and waterproof roofing felt are applied as quickly as possible to the roof trusses. However, the shingles may be applied some time later. In such a case, it is important that the roofing felt provide a watertight cover on the roof. Roofing felt, however, is not a tough material and is prone to rip on the nails, particularly when pulled laterally or in a sideways direction on the nails. Common washers reduce the tendency of roofing felt to pull over the heads of the nails in an axial direction but do little to resist sideways tears. Storms and winds present in inclement weather have a tendency to tear roofing felt off the roof, destroying the roofing felt, undoing the labor expended to apply the felt, and exposing the sub-roof to water penetration.
There have been some attempts to develop a washer for felt nails that has increased holding or gripping power, but these efforts have not been sufficiently successful. Rigid steel washers, in addition to being expensive, do not resiliently grip the felt. Washers that are quite resilient or flexible, such as the type used for insulation, provide poor edge gripping capabilities at the outer periphery of the washer. One prior washer specifically designed for roofing felt uses a downwardly cupped, molded low density polyethylene washer with a ring shank nail to provide some grip at the outer edges of the washer.
An object of the present invention is to provide an improved means for providing a superior holding or gripping force for roofing nails over a wide area of roofing felt while providing a superior waterproofing seal over the nail hole in the felt.